1. Field of the Invention
The subject invention generally relates to a polyurethane foam, a resin composition that may be used to form the polyurethane foam, and a method of forming the polyurethane foam on a substrate. More specifically, the subject invention relates to a resin composition including a combination of polyols that results in polyurethane foam having low surface friability, especially at low temperatures of less than or equal to 0° C.
2. Description of the Prior Art
Commercial and residential structures may be thermally and/or acoustically insulated by forming an insulating material, such as polyurethane foam, on the structures. The polyurethane foams comprise the reaction product of an isocyanate and a resin composition comprising a polyol or polyols, in the presence of a blowing agent.
To form the polyurethane foam on the structures, the resin composition and the isocyanate are combined in a mixing chamber of a spray gun to form a polyurethane composition. The polyurethane composition is then applied onto the commercial or residential structures to form the polyurethane foam through a polyol-isocyanate reaction. The polyurethane foam typically has an outer surface, a core, and an inner surface, which interfaces with the structures.
Unique problems arise when the polyurethane compositions are applied at low ambient temperatures, for example at less than or equal to 0° C., as is common during construction in cold climates. When the polyurethane compositions are applied at the low ambient temperatures, polyurethane foams have excessive surface friability and do not adhere well to structures. That is, the outer surface of the polyurethane foam crumbles and the inner surface of the polyurethane foams delaminates from the structures, thereby failing to provide adequate acoustic and thermal insulation.
The prior art has recognized various ways to decrease the surface friability of polyurethane foams, in general. For example, one way to decrease the surface friability of polyurethane foams is to increase the amount of catalyst used in the polyol-isocyanate reaction in an attempt to increase the speed of the polyol-ioscyanate reaction. However, the resulting polyurethane foam typically does not have enough cross-linking and will not foam to desired specifications.
Another way to decrease the surface friability of polyurethane foams is to select certain polyols for the resin composition. For example, as disclosed in U.S. Pat. No. 3,933,698 to Fuzesi et al., it is known in the art to form polyurethane foams comprising the reaction product of ethylenediamine-based polyols having ethylene oxide capping. Fuzesi et al. provides using from 8 to 50 parts by weight of an ethylene diamine-based polyol based on 100 parts by weight of total polyols used to form the polyurethane foam to achieve improved surface friability. The use of polyurethane foams comprising ethylene diamine-based polyols having ethylene oxide capping in the amounts set forth in Fuzesi et al. increases a polyol-isocyanate reaction temperature and conventional ozone-depleting blowing agents, such as hyrdrochlorofluorocarbons (HCFCs), are required to prevent scorching of the foam. Scorched foam is both aesthetically and functionally undesirable, as the scorched foam has excessive surface friability, separates from the substrate interface, and poses a fire risk. The conventional ozone-depleting blowing agents sufficiently cool the polyol-isocyanate reaction to prevent scorching.
However, new regulations, such as the Montreal Protocol on Substances That Deplete the Ozone Layer, statutorily mandate the phasing-out of ozone depleting agents, such as HCFCs, in favor of non-ozone depleting agents, such as hydrofluorocarbons (HFCs). The HFCs do not provide enough cooling to the polyol-isocyanate reaction, and the resulting foam often scorches.
Further, the polyurethane foams of Fuzesi et al. do not exhibit sufficiently low surface friability when the polyurethane composition used to form the polyurethane foam is sprayed at low ambient temperatures of less than or equal to 0° C. As such, there remains an opportunity to provide a polyurethane foam, a resin composition, and a method of forming the polyurethane foam on a substrate to remedy the surface friability and adhesion problems commonly experienced with such polyurethane foams, especially when the polyurethane composition used to form the polyurethane foam is applied at temperatures of less than or equal to 0° C.